在某个项目中图片下载并不是只有一个URL参数，还附带了其他的参数,因此自己利用AFNetworking下载图片，流程大致如下图：
在封装的网络请求中提供一个方法，在方法中根据传递过来的URL，判断在沙盒中是否存在这张图片，存在直接返回，不存在调用网络请求下载图片。下载成功存储在沙盒中，并返回给View中显示。
第一步在xxx.h文件中提供一个方法，例如如下方法
- (nullable UIImage*)productResource:(nonnull NSString*)resourceId;
第二步在xxx.m文件中实现该方法
- (nullable UIImage*)productResource:(nonnull NSString*)resourceId
{
UIImage* localImage = [[ResourceManager sharedManager] localImageById:resourceId];
if (localImage) {
#ifdef YDLL_DEBUG
NSLog(@"cached image is used, imageId: %@", resourceId);
#endif
return localImage;
}
NSDictionary* dictionary = [NSMutableDictionary dictionary];
[dictionary setValue:resourceId forKey:@"imageId"];
NSDictionary* requestDictionary = [RemoteDataResolver plainRequestFor:ENDPOINT_GETRESOURCE withDelegate:self withRequest:dictionary];
[[ResourceManager sharedManager] getResourceBy:requestDictionary andBy:resourceId];
return nil;
}
第三步在ResourceManager.h文件中提供获取沙盒图片方法和下载图片方法，以下面方法为例
// 根据相关参数下载图片
- (void)getResourceBy:(nonnull NSDictionary*)dictionary andBy:(nonnull NSString*)resourceId;
// 从沙盒中获取图片
- (nullable UIImage*)localImageById:(nonnull NSString*)resourceId;
第四步在ResourceManager.m文件中实现定义的方法
- (void)getResourceBy:(nonnull NSDictionary*)dictionary andBy:(nonnull NSString*)resourceId
{
[self.httpDownloadManager POST:[dictionary valueForKey:REMOTEDATARESOLVER_REQUESTURL_KEY]
parameters:[dictionary valueForKey:REMOTEDATARESOLVER_REQUESTBODY_KEY]
progress:^(NSProgress * _Nonnull uploadProgress) {
}
success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
if ([responseObject isKindOfClass:[UIImage class]]) {
NSString* resourcePath = [self.imageRoot stringByAppendingPathComponent:resourceId];
NSData* imageData = UIImageJPEGRepresentation(responseObject, 1.0);
[imageData writeToFile:resourcePath options:NSAtomicWrite error:nil];
id<ModelDelegate> delegate = [dictionary valueForKey:REMOTEDATARESOLVER_DELEGATE_KEY];
[delegate didSucceedOn:[dictionary valueForKey:REMOTEDATARESOLVER_ENDPOINT_KEY]
withResponseObject:responseObject
withRequestObject:[dictionary valueForKey:REMOTEDATARESOLVER_REQUESTBODY_KEY]];
} else {
id<ModelDelegate> delegate = [dictionary valueForKey:REMOTEDATARESOLVER_DELEGATE_KEY];
[delegate didFailOn:[dictionary valueForKey:REMOTEDATARESOLVER_ENDPOINT_KEY]
withRequestObject:[dictionary valueForKey:REMOTEDATARESOLVER_REQUESTBODY_KEY]];
}
}
failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
id<ModelDelegate> delegate = [dictionary valueForKey:REMOTEDATARESOLVER_DELEGATE_KEY];
[delegate didFailOn:[dictionary valueForKey:REMOTEDATARESOLVER_ENDPOINT_KEY]
withRequestObject:[dictionary valueForKey:REMOTEDATARESOLVER_REQUESTBODY_KEY]];
}
];
}
// 获取沙盒中图片
- (nullable UIImage*)localImageById:(nonnull NSString*)resourceId
{
NSString* resourcePath = [self.imageRoot stringByAppendingPathComponent:resourceId];
if ([[NSFileManager defaultManager] fileExistsAtPath:resourcePath]) {
NSData* imageData = [NSData dataWithContentsOfFile:resourcePath];
return [UIImage imageWithData:imageData];
} else {
return nil;
}
}
到此基本就完成了，不过这其中还有很多地方需要优化，比如下载过程中中断处理、图片过大等等。还需要不断的完善，仅提供一个处理思路。
